Re: HP G1005A question

Tim_Slattery@berlex.com
Thu, 25 Jun 1998 14:28:58 -0700

Jeanne,

I have been using an HP sequencer for many years, and have never had
to replace the teflon cap. As Joe pointed out the teflon threads are
very delicate and the vial must be tightened with caution. Unlike Joe,
I do not replace either the vials or the cap on a regular basis. I
just clean the vials with KOH. I only throw them away when I forget to
take them out of the heating block at the end of the day and etch the
insides as the KOH concentrates back to a solid.

Cross threading can be a problem, but you said that you lose seal
over time while the vial sits on the instrument. The only explanation
I can come up with is that you are overtightening the vial. Teflon
will cold-flow under pressure. This means that if the threads are
overtightened the plastic will slowly creep away form the point of
pressure. The result is that over time the threads will nolonger grip
the vial.

I think Joe gave a very good suggestion on how tighten the vial with
minimal risk. I just wanted to try to explain one of the symptoms that
you mentioned that hadn't been addressed.

Good luck.
--tks

Tim Slattery
Protein Biochemistry and Biophysics Department
Berlex Biosciences
tim_slattery@berlex.com


______________________________ Reply Separator _________________________________
Subject: HP G1005A question
Author: JEANNE I CORMAN 695-9610 <Jeanne.I.Corman@dupontmerck.com> at Internet
Date: 6/23/98 9:57 AM

To HP sequencer users:

I have had my G1005A sequencer 2 years and have had the flask cap assembly
replaced 5 times so far. The new assembly works fine with the initial flask put
in. (Although there were a couple of new assemblies that didn't work either.)
The flask stops turning in the cap and a seal is created. When I take that
flask out to clean or replace it and then put it or another one back in, the
flask just turns inside the cap and no seal is created. The loss of a good seal
will also happen over time while on the instrument, with no flask replacement.
The problem appears to me to be the o-ring between the
flask and the cap. It appears as though it gets distorted. I have had a lot
of downtime because of this problem. Has anyone else had this happen to them?
If so, what remedy do you use? Each time it has happened, HP ends up replacing
the whole cap assembly.

Thanks,

Jeanne